An environmentally-friendly vehicle has been developed globally, and vehicle emission standards for each country are being gradually reinforced. Further, vehicle makers have developed an environmentally-friendly diesel vehicle due to the regulation of carbon dioxide.
The exhaust gas emission of the diesel vehicle includes nitrogen oxides and particulate matter, and among them, a nitrogen oxide decreasing technique focuses to a lean NOx trap (LNT) and urea-selective catalytic reduction (urea-SCR). Particularly, the urea-SCR is useful to decrease nitrogen oxides discharged from a diesel engine of a large vehicle.
The urea-SCR is a selective reduction system which injects a harmless urea solution to an exhaust system, converts the injected urea solution into ammonia through pyrolysis, and causes the converted ammonia to react with a nitrogen oxide to convert the converted ammonia into a harmless component, such as water and nitrogen, and requires a storage system separately storing the urea solution.
The urea solution storage system includes a urea solution tank, a pump, an inlet, a pipe, a wire, and various kinds of sensors, and particularly, the pump requires a structure stably pumping a strong alkaline urea solution and a decrease in a vertical length of the urea solution tank.
A research to decrease a problem by improving a sealing structure of a power supply system, improving durability by preventing a rotor and a stator from being corroded due to a urea solution, effectively preventing a urea solution from being frozen, improving mounting stability of the sensors, and preventing impact according to a pressure increase when pumping a urea solution has been conducted.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention, and therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.